I'd definetely would rather have long interconnects and short speaker cables, preferably speaker cables hardwired to the speakers for best sound.
Regarding the initial question asking what are the possible reasons against monster integrateds. There are some engineering problems as others have mentioned (e.g., heat). But I think it's largely a marketing problem. If you could address the engineering issues, heat, channel spearation, isloation, power supplies, etc. How big would it be and how much would it cost, especially if done right? Who would buy it?
Another thing worth mentioning, as noted above is, how do you as a marketer deal with the stigma against integrateds and intergrateds with tuners (receivers). Some (most?) seems to perceive integrateds as being "compromised" and not truly "balls to the walls high end." outside of some engineering limitation previously noted, it *is* possible for a company's _flagship_ model to be an integrated or even a receiver (every audiophile should own a tuner, right?).
I like to draw a parallel with digital sources. There are still stigmas in some circles that separates (transport, D/D processor, DAC) are the "best." And for a while in digital-land (late 1990s, especially) this was true for the most part. Now we are seeing a resurgance (sp?) of one-box digital players being the best-of-the-best. I see posts all the time where some audiophile asks for advise on a DAC, and someone suggests that he instead look at one box players. Maybe it's not an exact parallel, but I find that reversal from separates in the digital realm interesting.
That stigma has been hard for me to shake, since 1996 I've always looked to digital separates. But it's taken some great one-box units to shake that long held belief of mine. I suppose the same could happen for integrateds, but perhaps the chicken-and-the-egg syndrone is too great. you have to build some great integrateds to change the perception, but who's willing to do that in a marketing climate perhaps hostile to top end integrateds? If you build it, will they come? I don't know.